Strain detection apparatus and method for radiological equipment

ABSTRACT

Apparatus and method are disclosed for detecting excess strain or failure in a main cable interconnecting a movable tower and counterweight assembly in a tiltable X-ray table. A secondary cable, substantially parallel to the main cable, is provided for supplementing the force exerted by the main cable structure between the tower and counterweight to a degree which is a function of the amount of strain occurring in the main cable. Changes in the amount of supplemental force provided by the secondary cable are sensed and used to produce an indication of the main cable strain. A supplemental force indication is accomplished by structure for holding a portion of the secondary cable in a transversely deflected position and by a spring actuated limit switch coupled to the deflected portion. The limit switch produces an indication in response to forces transverse to the length of the secondary cable exerted in the deflected portion, which forces result from increased tension on the secondary cable. The strain indication constitutes an audible signal produced by an audible signal generator in response to actuation of the limit switch. 
     The X-ray table has a top pivotable through the horizontal, and circuitry and apparatus for preventing further pivoting of the table top when the top has been moved to its horizontal position following the production of a strain indication. 
     RELATED APPLICATIONS AND PATENTS 
     1. Barrett, et al., U.S. Pat. No. 3,173,008, issued Mar. 9, 1975, under the title &#34;Spot Filmer.&#34; 
     2. R. C. Schiring, et al., U.S. Pat. No. 2,872,584, issued Feb. 3, 1959 under the title &#34;X-ray Apparatus.&#34; 
     3. R. C. Schiring, U.S. Pat. No. 2,997,585, issued Aug. 22, 1961 under the title &#34;Combined Image Amplifier and Fluoroscopic Screen Above X-ray Examination Table.&#34; 
     4. U.S. Pat. No. 3,916,203, filed Sept. 23, 1974, by E. A. Norgren, under the title &#34;X-ray Apparatus Including Counterbalancing Mechanism for Spot Filmer or the Like.&#34; 
     5. A concurrently filed patent application Ser. No. 668,624, for &#34;X-ray Table Lockout Apparatus and Method,&#34; by Ronald E. Lutz, et al. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     This invention is directed to X-ray apparatus, and more particularly, to improvement in an X-ray table tiltable about a pivot. The table has an imaging device (a spot filmer or the like) mounted on a tower. The tower is movably attached to the table. The table includes a mechanism for counterbalancing the mass of the tower when the table is tilted. 
     DESCRIPTION OF THE PRIOR ART 
     In X-ray examination apparatus, it is known to provide radiological systems including a so-called 90--90 X-ray table in which a table body and its asssociated top are tiltable on a pedestal about an axis transverse to the table length. Such tables are tiltable in either direction 90° from a position in which the table top is horizontal. Thus, the body of the table may be moved clockwise or counterclockwise from the horizontal until its top is vertical, or to any position between the vertical positions. Drive structure, including a reversible electric motor and circuitry to control it, is provided for effecting the desired tilting motion. One such table is that described and claimed in the referenced Schiring, et al., U.S. Pat. No. 2,872,584. 
     Other tables with lesser degrees of tiltability are also known. Some tables, for example, have a body which is tiltable in one direction from a top-horizontal position to a vertical position, and tiltable in the other direction to a so-called &#34;Trendelenburg&#34; position wherein the angle of the table is approximately 15° from the horizontal. 
     In most tiltable tables, a guide track is provided parallelling longitudinally the table top. A movable column or tower is slidably mounted on the guide track for movement on a path of travel which is longitudinal with respect to the table top. The column is also mounted for reciprocable rectilinear movement along a guide path transverse to the table top and normal to the column travel along the guide track. 
     The column supports an X-ray tube which is positioned beneath the table top and within the table body. One or more image producing X-ray responsive devices such as a spot filmer or an image intensification device are supported by a carriage, which is reciprocally mounted on the column for travel along a rectilinear path perpendicular to the plane of the table top. 
     These three paths of travel permit the carriage to be moved to any selected position over the table top and to any selected distance from the top within the limits of the respective paths of travel. 
     Since the motion of the column along the guide track has a vertical component when the table top is in a nonhorizontal position, at least one counterweight is used to counterbalance the column. The counterweight is desirable in preventing the heavy tower from tending to slide toward the lowered end of the X-ray table when tilted. 
     It is known to provide mechanical linkage between the tower and the counterweight to effect automatic counterbalancing of the weight of the tower as the tower is moved along the guide track, so that the table is always in a substantially balanced condition about its pivot on its pedestal. 
     According to one system, the counterweight is slidably mounted for longitudinal movement parallel to the guide track within the body of the table along a counterweight track. The counterweight and the tower (each weighing about 600 pounds) are connected together by two main or primary connectors made of suitable woven wire cable having an outside diameter of about 3/16 inch. 
     The cable portions are connected between the counterweight and the tower by way of their engagement with pulleys located at and within opposite ends of the table body. One portion of the cable is connected to one side of the counterweight, and extends outwardly around the pulley at one end of the table, and then inwardly to a point at which it is attached to the tower. The other portion of cable extends from the opposite side of the counterweight toward the other end of the table, around the pulley located there, and back toward an attachment to the tower. With this arrangement, motion of the tower in one direction causes an equal amount of motion of the counterweight in the opposite direction. The lengths of the two portions of cable, and the locations of the pulleys, are selected such that the counterweight is directly aligned with the table&#39;s pivot axis when the column is also so aligned, and so that the counterweight moves toward one end of the table when the tower is moved toward the opposite end. 
     An object of this invention is to provide apparatus and method for detecting and indicating the occurrence of excessive strain or failure in a main support of the X-ray table system. 
     SUMMARY OF THE INVENTION 
     This invention relates to a method and apparatus for sensing and indicating the occurrence of undesirable strain or failure in a main connector support structure interconnecting components of apparatus such as radiological equipment. An embodiment of the invention includes an auxiliary support structure connected for exerting a force supplementing that exerted by the main supporting structure in an amount which varies as a function of the strain on the main support structure. Such apparatus also includes apparatus for producing a signal in response to a change in the amount of the supplemental force exerted by the auxiliary support structure. 
     A more specific embodiment of the invention includes safety enhancement apparatus for use in an X-ray table having a movable tower and counterweight coupled for support by a first connector for effecting counterweight movement to adjustably counterbalance the X-ray table when tilted, notwithstanding the tower position. The embodiment comprises a secondary connector coupled substantially in parallel with the main connector for bearing an increased portion of the load between the tower and the counterbalance when strain occurs in the main connector, and means for indicating this increased tension on the secondary connector. 
     A more specific embodiment of the invention involves detector structure for sensing the increased tension on the secondary connector. This detector structure includes means for deflecting a portion of the secondary connector transversely from its path, so that the deflected portion produces a force component transverse to the path of the secondary connector which is a function of the degree of tension on the secondary connector. A resiliently mounted structure connects the deflected portion of the secondary cable to a limit switch. When the tension on the secondary connector increases to a predetermined extent, the transverse forces produced in the deflected portion of the secondary cable actuate the limit switch, to produce an indication of increased strain in the primary connector. 
     Because of differing inventorship involved in the system disclosed below, claims of this application have been limited to the general concepts regarding strain detection in radiological equipment, developed by two inventors. Other concepts, relating to interlock circuitry for such equipment were developed by the same two inventors plus one other, and are the subject of the referenced Lutz, et al., application. 
     These and other features of this invention will become apparent from an examination of the following description and drawings, in which:

A BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevational view, partially broken away, illustrating aradiological system incorporating an embodiment of the presentinvention;

FIG. 2 is a detailed plan view illustrating a portion of the embodimentof FIG. 1;

FIG. 3 is an elevational view of the structure shown in FIG. 2;

FIG. 4 is a detailed view illustrating another embodiment of theinvention incorporated in the structure of FIG. 1;

FIG. 5 is a detailed view, partially in cross-section of a portion ofthe structure shown in FIGS. 2 and 3;

FIG. 6 is a block diagram illustrating a portion of the radiologicalsystem shown in FIGS. 1 and 2;

FIG. 7 is a schematic drawing of a portion of the system shown in FIG.6;

FIG. 8 is a schematic drawing of another embodiment of that portion ofthe system shown in FIG. 7.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 illustrates a radiological system S incorporating the presentinvention. The system S directs X-rays through a subject and producesimages of the patterns of X-rays emerging from the subject.

The system S includes an X-ray table T for accommodating a subject to beexamined, such as a human body. The table T includes a pedestal P and atable body B attached to the pedestal. The system S also includes atower or column C mounted movably on the table body B which carries theapparatus for making the radiographs. The tower or column C supports anX-ray source X below the top surface of the table T, and also supportsan X-ray imaging apparatus I above the top surface of the table T forproducing radiographs from patterns of X-rays impinging on the imagingdevice I after passing from the source X upwardly through the subject.

The X-ray table body B, and the tower or column C mounted on the body,are tiltable, to enable changes in the attitude of the subject duringexamination. The body B is pivotally mounted on the pedestal P about apivot axis A. An electric motor M is connected to the table body by wayof drive mechanism (not shown) for furnising the motive power fortilting the table body B. Drive control circuitry D is connected to themotor M for actuating the motor M to pivot the table body B in a desiredfashion.

Mechanism is provided for facilitating the motion of the tower C in adirection longitudinal with respect to the table top defined by thetable body portion B. The table body B carries a guide track 10extending longitudinally with respect to the table top along theinterior of the table body.

The column C is movable along the longitudinal path defined by the guidetrack 10. A counterweight 12 is provided for counterbalancing the columnC with respect to the table B, irrespective of the position of thecolumn C along the guide track. The counterweight 12 is movablysupported in a counterweight track 14 extending along an inside surfaceof the table body B along a path generally parallel to that of the guidetrack 10.

The counterweight 12 is connected to the column C by way of two mainconnector portions 16, 18, which are engaged with a respective pair ofconnector pulleys 20, 22.

The main connector 16 is fastened to one end 24 of the counterweight 12,is engaged around the connector pulley 20 and is attached to the columnC in a manner described below. The main connector portion 18 is fastenedto the opposite end 26 of the counterweight 12 and is engaged with theconnector pulley 22 and connected to the column C, also in a fashiondescribed below. When the column C is moved to the right as illustratedin FIG. 1, the counterweight 12 moves to the left, in an equal amount,and vice versa. The counterweight C has a weight comparable to that ofthe column C, with the X-ray source X and the imaging apparatus Imounted thereon.

The X-ray table T is suitably embodied by an X-ray table manufactured byPicker Corporation of Cleveland, Ohio, having the catalog number Series1240, or Series 1243, and designated by the trade mark "Galaxy." Theimaging apparatus I is of known construction, and may suitably beembodied by a spot filmer (referred to above) or by an imageintensification device, also known in the art. Likewise, the X-raysource X is of known construction and selectable by one of ordinaryskill.

X-rays tables such as illustrated in FIG. 1 differ slightly. One typeX-ray table, shown in FIG. 1 specifically, is capable of tilting eitherclockwise or counterclockwise in any amount up to 90°. Another type ofsimilar X-ray table, such as a Picker Catalog No. Series 1241, or Series1244, is capable of tilting in a clockwise direction, as viewed in FIG.1, in any amount up to 90°, and in a counterclockwise direction in anyamount up to only about 15°.

Apparatus is provided in the X-ray table T to detect and indicate theoccurrence of excessive strain or failure in the main connector portions16, 18, which may result from overloading or deterioration of theseconnector portions. This apparatus includes a set of secondaryconnectors 30, 32 coupling together the counterweight 12 and the columnC, to supplement the force exerted by the main connector portions 16,18, and by detector apparatus 34 for sensing and indicating increases inthe forces exerted by the secondary connector portions 30, 32.

The secondary connector portions 30, 32 are respectively connectedbetween the counterweight 12 and the column C by a pair of secondarypulleys 20a, 22a, along paths which are generally parallel to those ofthe main connector portions 16, 18. Preferably, the secondary connectorportions 30, 32 are embodied by woven wire cable having a diameter ofapproximately 1/8 inch and a tensile strength of approximately 2,000pounds. Each of the secondary connectors 30, 32 is a length selectedsuch that secondary connectors 30, 32 are stressed to only a relativelysmall fraction of the stress forces normally exerted on the mainconnector portions 16, 18.

The detector apparatus 34 includes structure for holding a portion ofeach of the secondary connectors 30, 32 in a deflected position relativeto the general path of the respective secondary connectors. The detector34 also includes structure for sensing the amount of force transverse tothe path of each secondary connector which is exerted by the deflectedportion, and which is a function of the amount of tension on thesecondary connectors.

If one of the main connectors 16, 18 is stretched, or "strained" byoverloading, deterioration, or damage, a portion of the load borne bythe main connector is transferred to its associated secondary connector.This increase in tension is sensed by the detector apparatus 34, whichproduces an indication of that increase, warning of possible strain onthe associated main connector.

The detector apparatus 34 includes a detector carriage 36 having mountedtherein pulley structure (described below) for deflecting the secondaryconnectors 30, 32, and a pair of resiliently biased limit switch units38, 39 (FIG. 2) connected to the deflected portions of the cables forsensing increases in the tension on the associated secondary connectors.The detector carriage 36 also provides anchoring structure for both themain and secondary connectors.

The detector carriage 36 is mounted affixed with respect to the column Cby transversely extending carriage structure including a pair of rods41, 42. The rods 41, 42 each extend transversely across the table body Band are coupled to the column C by suitable structure (not shown) whichmaintain the rods 41, 42 longitudinally movable with the column C. Thedetector carriage 36 is integrally connected to the rods 41, 42 and isfixed transversely with respect to the table body B. The detectorcarriage anchors both the main and secondary connectors 16, 18, 30, 32.

FIGS. 2 and 3 show a detailed embodiment of the detector apparatus 34employed in connection with the table of FIG. 1. Both the mainconnectors 16, 18 and the secondary connectors 30, 32 are anchored onthe detector carriage 36. The main connector portion 16 is passed over apulley 44 and anchored at a bolt anchor terminal 46. The end of the mainconnector 18 attached to the detector carriage 36 is also passed overthe pulley 44 and anchored similarly at a bolt anchor terminal 48.Similarly, the respective ends of the secondary connectors 30, 32 arepassed in opposite directions over a pulley 50 and anchored respectivelyat anchor terminals 52, 54.

The apparatus for deflecting a portion of the secondary connectors 30,32 is also attached to the detector carriage 36. A portion of thesecondary connector 30 is deflected by the combination of a pulley 55,over which the connector is passed, and a pulley 56, attached to thelimit switch unit 38. The limit switch unit 38 applies tension to thepulley 56 (upwardly in FIG. 2) which works against the pulley 55 and thepulley 50 to deflect a portion of the secondary connector 30.

In similar fashion, the secondary connector 32 is engaged with anddeflected by the coaction of the pulley 50, a pulley 57, and by a pulley59 attached to the limit switch unit 39.

The limit switch units 38, 39 are substantially identical inconstruction. Accordingly, only the limit switch unit 38 will bedescribed in detail here, and it will be understood that theconstruction of the limit switch unit 39 is substantially identical tothat of the limit switch unit 38.

The limit switch unit 38 includes a resilient structure 58 having oneend fastened to the detector carriage 36, and its other end to thepulley 56. The pulley 56 is rotatably fastened to a plate 61 which isslidably mounted for vertical movement (FIG. 2) on the carriage 36. Theresilient structure 58 biases the pulley 56 and plate 61 upwardly inFIG. 2. The plate 61 is connected by suitable connecting structure toone end of a sleeve 63 mounted for axial movement. The sleeve 63 has atapered portion 67 which actuates a limit switch 60 when the upwardlybiased sleeve 63 has been pulled down a predetermined distance bytransverse downward forces exerted on the pulley 56 by tension of thesecondary connector 30.

The resilient bias of the structure 58 in an upward direction isobtained by the use of a number of Belleville washers, e.g., 64 (FIG. 5)inserted within a housing 71 of the structure 58 and coaxial with aflanged rod portion 73. The housing 71 is attached to the pulley 56 by abored flange 71a, and the rod 73 is attached to the carriage 36 bythreads 73a.

In operation, if strain occurs in one of the main connectors 16, 18, thelengthening of the affected connector will cause the transfer of atleast part of the load borne by the main connector 16 of the associatedsecondary connector. This occurrence will increase the tension on thesecondary connector, and this increased tension will increase thedownward force on the pulley component of the associated one of thelimit switch units 38, 39. In response to this increased downward forceand lessening of the deflection of the secondary connector, the limitswitch unit actuates the limit switch 60, which in turn is connected toactuate an audible signal generator 66, such as an electric buzzer orbell, and other circuitry discussed below.

Means is provided for adjusting the operative engagement between thelimit switch 60 and the tapered portion 67 of the sleeve 63. The sleeve63 has an eccentrically-shaped cross-section. The engagement between thetapered sleeve portion 67 and the limit switch 60 is adjustable byrotating the sleeve 63 about a longitudinal axis of the sleeve. Thisadjustability facilitates compensation for dimensional inaccuraciesamong the various parts of the detector assembly 34. This feature alsoenables the adjustment of the predetermined amount of main connectorstrain and secondary connector tension required to actuate the limitswitch 60.

A variant of the X-ray table T, shown in FIG. 1, as discussed above, cantilt in the clockwise direction only to a maximum amount of about 15°from the horizontal. Accordingly, in the variant embodiment, there is noneed to provide strain detection features such as discussed above inconnection with the main connector 16 and its associated secondaryconnector 30. This is because the main connector 16 cannot be placedunder nearly as much tension as the connector 18.

Accordingly, the detector apparatus used in connection with the variantembodiment of the table T is simpler than that associated with the firstdiscussed embodiment.

FIG. 4 shows a slightly different embodiment of the detector apparatus34 usable in connection with the variant embodiment of the table T, theso-called "90-15" table. Briefly described, the detector apparatus ofFIG. 4 substantially identical to that of FIG. 3 except for the exlusionof all the components thereof associated with stress detection in thesecondary connector 32. That is, the embodiment shown in FIG. 4 is thesame as that of FIG. 3, and operates similarly, with the exception ofthat the limit switch 39 and the pulleys 59, 57 are omitted.

FIG. 6 is a block diagram illustrating the drive control circuitry D andthe manner of its connection to the drive motor M. The drive controlcircuitry D actuates the drive motor M to tilt the X-ray table body B ina predetermined direction and to a predetermined degree. Unlessotherwise indicated herein, the components of the drive controlcircuitry D are of known structure and arrangement, and are embodied inthe above-referenced "Galaxy" X-ray tables.

The motor M is suitably embodied by an AC or DC motor having sufficientpower to drive the X-ray table body over its desired motion increment.The motor M has armature and field windings connected such that themotor M is reversible, in response to the actuation of certain relaycontacts (not shown) connected to the motor M and contained in a motorcontrol component 70.

The relays of the motor control component 70 are actuated to operate themotor M by the depression of an actuator button 72, which is suitablyembodied by a switch such as a foot switch operable to selectively closeone of two sets of switch contacts for applying power for actuating themotor M to operate in a direction which is determined by which of theswitch contacts of the actuator 72 are closed.

The actuator 72, in addition to operating the motor control component70, operates a start-up circuit 74. The start-up circuit 74 includescircuitry which inserts a removable capacitance (not shown) in thearmature windings of the motor M for a predetermined period of timefollowing operation of the actuator button 72, after which thecapacitance introduced by the start-up circuit 74 is removed from thearmature circuit.

The motor M operates a table tilt mechanism linkage 77 to controllablytilt the table body B in accordance with the speed and duration ofoperation of the motor M.

A fail-safe mechanical brake 76 (electrically operated) is used toprevent motion of the table body B under any circumstance in which poweris not applied to the motor M.

Limiting circuitry 80 responds to the position of the table body B toautomatically cut off electric power from the motor M when the tablebody B has reached a limit of its permitted tilted excursion. Thelimiting circuitry 80 includes suitable limit switches of knownconstruction coupled to the table tilt mechanism 77 and responsive tosensing the table body B reaching its maximum permitted excursion todisable the motor M from further operation in its immediately previousoperating direction.

Horizontal stop circuitry 82, also of known design, responds to thetable body B reaching its top-horizontal position to operate upon themotor control circuitry to deactuate the motor M, until a switch contactof the actuator 72 is opened and re-closed. The horizontal stopcircuitry 82 is useful in enabling an operator of the table T to returnthe table body B to its top-horizontal position following tilting toother positions by merely depressing the actuator 72 until the top movestoward the horizontal and stops upon reaching it. This featureeliminates the necessity for "cut and try" methods of returning thetable top to the horizontal position.

In operation, the horizontal stop circuitry 82 causes the motor M tostop when the table body B reaches its top-horizontal position afterhaving been rotated from a tilted position. The horiziontal stopcircuitry 82, however, does not prevent further operation of the tabletilt mechanism 77. It merely serves as a means to halt the table body Bat its desired horizontal position. When the actuator 72 is againactuated, the motor M again responds to initiate a new tilting motion ofthe table body B in the direction corresponding to which of the switchcontacts of the actuator 72 is re-closed.

The previously described circuitry of FIG. 6 is, as mentioned above,already known in the art, and therefore has not been described in detailhere.

The embodiment of the presently disclosed invention also includesinterlock circuitry 100. The interlock circuitry 100 responds to anindication of undesirable strain on one of the main components 16, 18 todisable the motor M to prevent the further tilting of the table body Bafter it reaches the horizontal position following an indication of suchstrain. Once the interlock circuitry 100 has disabled the motor M, thetable body B cannot again be tilted by operation of the actuator 72until the strained condition which is indicated has been corrected.Meanwhile, however, the other components of the X-ray table T remainfully operable, insofar aas they can be used for the examination ofsubjects with the table top in its horizontal position.

FIG. 7 is a schematic diagram illustrating one embodiment of theinterlock circuitry 100. The interlock circuitry 100 performs twofunctions. First, it responds to the sensing of a strained condition ofpredetermined magnitude in one of the main connectors 16, 18 to preventthe table body B from being further tilted after the table body has beenreturned to its horizontal position. Second, the interlock circuitry 100actuates the audio signal generator 66 to emit a warming signalconstantly until the table body B is returned to its top-horizontalposition after the sensing of the strained main connector.

The lockout circuitry 100 operates in response to a pair of actuatorswitches 102, 104, the position of a level control switch 106, and thecondition of a detector switch 110. The switches 102, 104 are normallyopen switches, which can be separately closed by actuation of theactuator 72. The level control switch 106 constituting a portion of thehorizontal stop circuitry 82. The level control switch contacts itsupper terminal, as shown in FIG. 7, when the table top of the body B isin a horizontal position. At all other times, the level switch contactsits lower contact. The detector switch 110 is normally in contact withits lower terminal, as viewed in FIG. 7, but, in response to the sensingof a strained condition in a main connector, moves to contact its upperterminal. The detector switch 110 is responsive to the actuation of oneof the limit switches 60 in connection with one of the limit switchunits 38, 39.

The switches 102, 104 are connected in series with one of two operationrelays 112, 114, respectively, which constitute part of the motorcontrol circuitry 70. The operation relay 112 actuates relay contacts(not shown) which actuate the motor M to operate in one direction.Actuation of the operation relay 114 actuates a set of relay contactsassociated with the motor M to cause the motor M to operate in the otherdirection.

When the switch 102 is closed, for example, by operation of the actuator72, the relay 112 is actuated, causing the motor M to tilt the tablebody B in a predetermined direction. If the table body B is alreadytilted, the switch 106 will contact its lower terminal, and normally theswitch 110 will contact its lower terminal.

Under these conditions (no strain detection and table body B tilted),current is shunted around the switch 110 through a lead 116 and throughthe switch 106, and the table body B is tilted by operation of the motorM.

When the table body B has tilted enough to bring the table top to ahorizontal position, the switch 106 moves to contact its upper terminal.Current can no longer flow through the lead 116, and current thereforeflows through the switch 110 and through a lockout relay 120.Energization of the lockout relay 120 reduces voltage to the relays 112,114 to a degree sufficient to deactuate these relays and cut off powerfrom the motor M, while the relay 120 is energized.

The lockout relay 120 moves a relay contact 122 to contact its lowerterminals as viewed in FIG. 7, which in turn causes the actuation of alatching relay 124 and a bypass relay 126. Actuation of the latchingrelay 124 closes a normally-open relay contact 130 which latches in therelays 124, 126, by virtue of the fact that the switch 106 contacts itsupper terminal in this condition.

This condition, in which the lockout relay 120 is actuated, halts thetilting operation of the table body B as the table body is tiltedthrough the horizontal. Under normal circumstances, however, thedeactuation and reactuation of the actuator 72 causes the immediateresumption of tilting motion of the table body B. This resumption ofmotion is enabled by bypass circuitry in the interlock circuitry of FIG.7.

The bypass circuitry includes the bypass relay 126 and a normally-openrelay contact 134. After the table body B has reached its top-horizontalposition and the closed one of the switches 102, 104 is released,opening the switch, the application of power to the lockout relay 120ceases, and the contact 122 resumes its normal condition, i.e., itcontacts its upper terminal. Since the bypass relay 126 is actuated, thenormally-open contact 134 is closed, furnishing a current path from therighthand end of the switch 110, through the contact 134 and 122. Thus,when one of the switches 102, 104 is re-closed, the current flowingthrough the associated relay 112, 114, rather than being directedthrough the lockout relay 120, is simply shunted through the contacts134, 122. This enables the continued tilting operation of the table bodyB.

The above discussion in connection with FIG. 7 has assumed that theswitch 110 was closed, which is the case when no excessive mainconnector strain has been detected. In instances in which excessivestrain has been detected, the switch 110 is opened in response toactuation of one of the limit switch units 37, 39. The opening of theswitch 110 disables the effect of actuation of the bypass relay 126, bycutting off current flow through the contacts 134, 122.

Under these conditions, the operation of the system prior to the tablebody B reaching its top-horizontal position is the same as describedabove. Under such conditions, when one of the switches 102, 104 isclosed, while the body B is n a nonhorizontal position, the currentflowing through the associated relay 112, 114 is shunted to ground byway of the switch 106 and the lead 116, until the table reaches itshorizontal position. At that point, the switch 106 changes its positionto contact its upper terminal.

From this point on, operation of the circuit with the switch 110 in itsopen condition is different from that described above. In thiscondition, the bypass circuitry including the contacts 134, 122 arerendered ineffective, and it becomes impossible to actuate the motor Mto operate the table further until the detected cable strain conditionis corrected, closing the switch 110. The opening and re-closing of oneof the switches 102, 104 thus has no effect on the operation of thesystem. This is true because the open switch 110 prevents current fromflowing from the relays 112, 114 through the contacts 134, 122 when theswitches 102, 104 are opened and re-closed.

The circuitry of FIG. 7 also actuates the audio signal generator 66 toproduce an audio signal indicating cable strain when the switch 110 isopened. The production of this signal continues through the entire timesubsequent to the opening of the switch 106 in which the table body Bcontinues in a nonhorizontal position, and the audio signal generationceases only when the table has reached a horizontal position. The audiosignal generator 66 is shown in FIG. 7 as connected between theelectrical lead 140, serving as a power source, and an upper terminal142 of the switch 110. The common of the switch 110 is connected to thelead 116.

When the switch 110 is closed, no current can flow through the audiogenerator 66. When the switch 110 is opened, however, the connection tothe upper terminal 142 furnishes a current path to the audio generator66 through the lead 116 and to the switch 106, as long as the table bodyB is in a tilted position. When, however, the table body B reaches thehorizontal position, the switch 106 contacts its upper terminal,breaking the connection between the lead 116 and ground, which causesthe audio generator to cease its signal generation.

FIG. 8 shows an alternate embodiment for the relay circuitry foraccomplishing the analogous functions as are accomplished by thecircuitry of FIG. 7, in connection with the so-called "90--90 degree"X-ray table. This table, as explained above, has two auxiliaryconnectors 30, 32 and two limit switch units 38, 39. The switchesactuated by the limit switch units 38, 39 are illustrated in FIG. 8 asswitches 150, 152. Each of these switches remains closed in the absenceof an excessive strain detection, and each switch opens in response tothe detection of a strained condition in its associated secondaryconnector. As long as these switches 150, 152 are closed, a relay 154 isenergized. The relay 154 is connected to a series of contacts (notshown) which enable the operation of the motor M to operate the tiltabletable body B. The relay 154 is thus energized under normal operatingconditions in which there is no connector failure.

FIG. 8 also shows a set of switches 160, 162 which correspond to theswitches 102, 104 in the previously discussed figure. When one of theswitches 160, 162 is closed, by actuation of the switch actuator 72, acurrent path is provided from a lead 164 through one of the isolationdiodes 166, 167 and a lead 168. The operative effects of the switches160, 162 are analogous, and only the operation of the switch 160 isdiscussed here, for purposes of simplicity.

The lead 168 is connected to a level switch 170 which is analogous tothe level switch 106 in the previous figure. The level switch 170contacts its upper terminal in conditions in which the table body B isin a nontop-horizontal position, and contacts its lower terminal whenthe top reaches a horizontal position. Thus, when the switch 160 isclosed a current path is provided through the level switch 170 actuatinga relay 174. Actuation of the relay 174 closes a normally-open latchingcontact 176, which enables the actuation of the relay 174 for as long asone of the switches 160, 162 is closed, even after the switch 170 hasmoved to contact its lower terminal in response to the reaching of ahorizontal position by the table top of the body B.

Also, when the switch 160 is closed, power flows through an actuatingrelay 180 which is connected to relay contacts associated with the motorM causing the motor M to operate to tilt the table top. A current paththrough the relay 180 is furnished by a normally-closed relay contact182 associated with the relay 186 or a relay contact 188 associated withthe relay 174.

When the table top reaches its horizontal position, the switch 170contacts its lower terminal. Since the latching relay contact 176 isclosed by operation of the relay 174, the current path through the relay174 remains unbroken, and this relay remains in its actuated conditionfor as long as the closed one of the switches 160, 162 continues to beclosed. The current path through the switch 170, however, isinterrupted.

When the switch 170 moves to contact its lower terminal in response tothe table top reaching the horizontal position, a relay 186 is actuatedby a current passing through a normally-open contact 188 (which is heldin its closed condition by actuation of the relay 174). Actuation of therelay 186 causes the opening of the normally-closed contact 182, thuscutting off power from the actuating relay 180, and causing the motor Mto halt its operation.

When one of the switches 160, 162 is then opened and re-closed, themotor M is actuated by the relay 180, 181 to resume tilting motion ofthe table body B. When the closed one of the switches 160, 162 isopened, the relay 174 becomes deactuated. The latching relay contact 176opens and the contact 188 moves to contact its upper terminal. Since therelay 186 is deactuated, the normally-closed contact 182 returns to itsupper terminal. The movement of the contact 188 to contact its upperterminal again furnishes a current path through the actuation relay 180such that, when the switch 160 is re-closed, power flows through therelay 180 and the motor M is actuated to tilt the table body B away fromthe horizontal.

Operation of the system is different when a strained condition issensed, and one of the switches 150, 152 is opened, deactuating therelay 154. When the relay 154 is deactuated, a normally-open relaycontact 190 (held open by energization of the relay 154) is caused tomove to its normally-closed condition.

If the table body B is in a tilted position, and the switch 170 contactsits upper terminal, closure of the switch 160 causes current flowthrough the relay 174, actuating the contact 176 to close. Power foractuating the operation relay 180 flows from the closed switch 160through the relay 180 and the normally-closed contact 182. When,however, the table body B reaches its top-horizontal position, theswitch 170 moves to contact its lower terminal, actuating the relay 186.Actuation of the relay 186 opens the normally-closed contact 182,interrupting the current path through the relay 180, causing the motor Mto become deactuated, and unable to tilt the table body any further.

Under these conditions, the opening and re-closure of one of theswitches 160, 162 does not effect the continued motion of the table bodyB, as in the case of the previous example.

The earlier deactuation of the relay 154 causes the closing of thenormally-closed relay 190. The closure of this relay 190 assures thatthe relay 174 will be continuously actuated from that time on. Thisactuation closes the latching relay contact 176, and also moves therelay contact 188 to contact its lower terminal causing the actuation ofthe relay 186. The relay 186 causes the opening of the normally-closedcontact 182, such that even if the switch 160 is re-closed, there is nopath for current to flow through the operation relay 180. Thus, when astrained condition is detected, the circuitry of FIG. 8 entirelydisables the motor M from operation, when the top-horizontal position isattained, until the strained condition is corrected, causing the closureof the opened one of the switches 150, 152.

As in the case of FIG. 7, the existence of a strained condition causesthe actuation of the audio generator 66, as long as the table body B hasits top in a nonhorizontal tilted position. The production of the signalgenerated by the generator 66 ceases only when the table top is returnedto a horizontal position.

It has been seen, from the discussion above, that the relay 154 isactuated during any condition in which there is no strain detected anddeactuated when a strain is detected. The relay contact 194 is anormally-closed contact which is maintained in its open condition aslong as the relay 154 is actuated, as during normal unstrainedoperation.

Additionally, a relay contact 196 is provided which is normally-closed,and which is opened in response to actuation of the relay 186. As hasbeen seen from the above discussion, the relay 186 is actuated only whenthe top of the table body B is in a horizontal position. Thus, the audiogenerator 66 is actuated whenever the following two conditions prevail:(1) the relay 154 is deactuated indicating a strained condition in oneof the secondary connectors; and (2) the relay 186 is not actuated,indicating that the table top of the body B is in a nonhorizontalposition. When the table body B reaches a horizontal position the relay186 is actuated, thus opening the contact 196 and ceasing operation ofthe audio signal generator 66.

It is to be understood that the above description is intended asillustrative rather than exhaustive of the invention. Those of ordinaryskill in the art may make certain adaptations, changes, or modificationsto the invention as disclosed here without departing from the spirit ofthe invention or the scope of the appended claims.

What is claimed is:
 1. Apparatus for detecting stress in a primarysupport structure for exerting primary force for supporting a componentof medical diagnostic equipment, said apparatus comprising:a. anauxiliary support structure connected to said component forindependently exerting force on the component for supplementing theprimary supporting force of the primary support structure in an amountwhich varies in response to the occurrence of strain in said primarysupport structure; and, b. apparatus for producing a signal in responseto a change in the amount of said supplemental force exerted by saidauxiliary support structure.
 2. The apparatus of claim 1, furthercomprising:apparatus responsive to said change in supplemental forceexertion for restricting a subsequent operation of said radiologicalequipment.
 3. Safety enhancement apparatus for use in an X-ray tablehaving a movable tower for supporting radiological apparatus and acounterweight coupled to the tower by a first connector under tensionfor effecting counterweight movement for adjustably counterbalancing theX-ray table with respect to the position of the tower, said safetyapparatus comprising:a. a secondary connector coupled substantially inparallel with said first connector for bearing an increased portion ofthe tension load between the tower and the counterweight when strainoccurs in the first connector; and, b. means for indicating saidincreased tension on said secondary connector.
 4. Apparatus fordetecting strain in a primary support structure for a component of aradiological system, the primary support structure including two firstconnectors connected to the component, said apparatus comprising:a. twosecondary support structures each comprising a second connectorconnected in parallel with a different one of said two first connectors;and, b. apparatus for separately detecting a predetermined variation inthe amount of force exerted on the component by each of the secondconnectors and for producing a signal in response to the occurrence ofsaid predetermined variation.
 5. Apparatus for detecting stress in aprimary structure for exerting primary force for supporting a componentof mechanized equipment, said apparatus comprising:a. an auxiliarysupport structure connected for independently exerting forcesupplementing the primary supporting force of the primary supportstructure in an amount which varies in response to the occurrence ofstrain in said primary support structure; and, b. apparatus forproducing a signal in response to a change in the amount of saidsupplemental force exerted by said auxiliary support structure. 6.Apparatus for detecting stress in a primary support structure forexerting primary force for supporting a component of radiologicalequipment, the primary support structure including a cable connected tosaid component, said apparatus comprising:a. an auxiliary supportstructure including a different cable connected to said component andextending along a path substantially parallel to that of the primarysupport cable structure, said auxiliary support cable structure beingconnected for exerting force supplementing the primary supporting forceof the primary support cable structure in an amount which varies inresponse to the occurrence of strain in said primary support cablestructure; and b. apparatus for producing a signal in response to achange in the amount of said supplemental force exerted by saidauxiliary support structure.
 7. Safety enhancement apparatus for use inan x-ray table having a movable tower for supporting radiologicalapparatus and a counterweight coupled to the tower by a first connectorunder tension for effecting counterweight movement for adjustablycounterbalancing the x-ray table with respect to the position of thetower, and safety apparatus comprising:a. a secondary connector coupledsubstantially in parallel with said first connector for bearing anincreased portion of the tension load between the tower and thecounterweight when the strain occurs in the first connector; and b.apparatus for indicating said increased tension on said secondaryconnector comprising:i. structure engaged with the secondary connectorfor deflecting a portion of the secondary connector so that increasedtension on said secondary connector produces forces in its deflectedportion transverse to the path of said secondary connector through saiddeflected portion; ii. an electrical switch coupled to sense theoccurrence of said transverse forces on said secondary connector; iii. asecond deflector means for deflecting a second portion of said secondsecondary connector so that increased tension on said secondaryconnector in said second deflected portion produces forces transverse tothe extension of the second deflected portion, and iv. a secondelectrical switch coupled to sense said increased tension in said seconddeflected portion.
 8. Safety enhancement apparatus for use in an x-raytable having a movable tower for supporting radiological apparatus and acounterweight coupled to the tower by a first connector under tensionfor effecting counterweight movement for adjustably counterbalancing thex-ray table with respect to the position of the tower, said safetyapparatus comprising:a. a secondary connector coupled substantially inparallel with said first connector for bearing an increased portion ofthe tension load between the tower and the counterweight when strainoccurs in the first connector, and b. means for indicating saidincreased tension on said secondary connector, said tension indicatingmeans comprising:i. structure engaged with the secondary connector fordeflecting a portion of the secondary connector so that increasedtension on said secondary connector produces forces on its deflectedportion transverse to the path of said secondary connector through saiddeflected portion,and ii. an electrical switch coupled to sense theoccurrence of said transverse forces on said secondary connector.
 9. Theapparatus of claim 15, wherein said deflecting means comprises:a pulleyguide structure engaged with said secondary connector, and b. a springactuated microswitch coupled to said deflected portion for producing anindication of the occurrence of said transverse forces in response to apredetermined extension of said spring.
 10. Safety enhancement apparatusfor use in an x-ray table having a movable tower for supportingradiological apparatus and a counterweight coupled to the tower by afirst cable connector under tension for effecting counterweight movementfor adjustably counterbalancing the x-ray table with respect to theposition of the tower, said safety apparatus comprising:a. a secondarycable connector being of lighter gauge than said first cable connectorcoupled substantially in parallel with said first cable connector forbearing an increased portion of the tension load between the tower andthe counterweight when strain occurs in the first connector, and b.means for indicating said increased tension on said secondary connector.11. Apparatus for detecting stress in a primary support structure forexerting primary force for supporting a component of medical diagnosticequipment, said apparatus comprising:a. a single cable auxiliary supportstructure connected for exerting force supplementing the primarysupporting force of the primary support structure in an amount whichvaries in response to the occurrence of strain in said primary supportstructure, said auxiliary support structure being connected andconstructed to be capable of exerting sufficient supplemental force tosupport said component independently, and b. apparatus for producing asignal in response to a change in the amount of said supplemental forceexerted by said auxiliary support structure.
 12. The apparatus of claim11, further comprising:apparatus responsive to said change insupplemental force exertion for restricting a subsequent operation ofsaid radiological equipment.
 13. A medical diagnostic systemcomprising:a. an x-ray table tiltable about a horizontal axisperpendicular to its length; b. a tower mounted on the table formovement longitudinally along the table; c. an x-ray source on the towerfor directing x-rays through a subject on the table; d. a counterweightmovably mounted to the table; e. primary and secondary support cablesconnecting the counterweight and the tower for coordinating movementtherebetween wherein the counterweight facilitates balance of thetiltable table about its axis notwithstanding movement of the tower;i.said primary support cable being for exerting a primary support forcebetween the counterweight and the tower; ii. said secondary cable beingconnected directly between the counterweight and tower for exertingindependently a supplemental force which varies in response to theoccurrence of strain in the primary cable, and iii. apparatus forrestricting the tilting of the table in response to the exertion of apredetermined amount of supplemental force by the secondary cable. 14.Apparatus for supporting a suspended load, comprising:a. a primary cableconnected for supporting the load; b. a secondary cable connected to theload independently of other support cables, said secondary cablesupplying a supplemental supporting force which is a function of theamount of strain in the primary cable, and c. apparatus responsive tothe exertion of a predetermined amount of supplemental force by thesecondary cable to produce a warning signal.